It's not an easy task for any ISPs -- just Google: 6to4, 6over4, etc...

It is easy with equipment that supports native/dual-stack IPv6. IPv6 support has become a standard feature in practically all core routers more than five years ago and it is standard in all DOC3 equipment so in principle, cablecos with DOC3 have all the building blocks for native/dual-stack IPv6, no need for that 6to4/4to6/etc. junk.